He did a big mistake by overruling the advice of his officers who had advised him not to take the southern route as it was under complete control of Sher Shah Suri, who was looking for an opportunity to come face to face with the Mughal Emperor.

This route was on surveillance by vigilant Afghan scouts and every little movement of the Mughal army on this route was communicated. Consequently, Sher Shah Suri was informed of this movement and the Mughal Emperor Humayun was stopped and was obliged to cross the Ganga back to its northern bank.

On reaching chausa, Humayun was informed about Sher Khan who by this time had reached the neighbourhood. Hearing this, the Mughals wanted to attack the Afghans, who were tired because of prolonged journey but Humayun declined the advice of attacking them at once and decided to re-cross the river to its southern bank. This was his second mistake as it gave time to Sher Shah Suri to plan the defence and also gave much needed rest to his men.

Both the armies remained encamped face to face for three months from April to June 1539, but purposely delayed the attack. However, there were efforts for peaceful settlements from both sides which did not help. Thereafter came the rainy season, which Sher Shah Suri thought could be of advantage to him as he knew that the Mughals had encamped on a low land between the two rivers and were prone to flooding.

Sher Shah reacted as soon as the rains set in and along with his son Jalal Khan and his general Khawas Khan he made a surprise attack on the Mughals from three directions and defeated the Mughal army. Most of the Humayun’s men were either killed or drowned, many died of disease, hardship and surprise attack from the enemy and Humayun who was not in the position to face the attacks, fled towards Agra, with only a few soldiers left with him.